The present invention relates to medical scanning. More particularly the present invention relates to a method and apparatus of interactive positioning by registration and alignment of a medical scanner""s image coordinate set with the physical coordinate set so as to facilitate accurate positioning during medical scanning and/or surgical procedure.
When performing medical scanning procedure, precision in localization of different objects or areas within the patient""s tissue is of crucial importance. This is especially true for surgical procedures performed in a closed body area, when visualization of the target is impossible (i.e. within the patient""s head, stomach etc.). One example is brain surgery, where knowledge of the exact localization of various anatomies allows planning of the procedure and avoiding unnecessary damage to healthy surrounding tissue. Recent diagnostic methods such as computerized tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET), nuclear medical apparatus and other medical scanning methods allow accurate pre-operative diagnosis. Nevertheless, these pre-operative pictures are of limited relevance once a surgical procedure is performed since they depend on the coordinates of the patient which might change during the course of operation due to different positioning or on brain shift during surgery.
To overcome this problem, stereotactic surgery and navigation are commonly used and are based on pre-operative images and on rigid markers fixed to the patient. Still, registration of the patient is always needed to compare pre-operative scans and the current situation during surgery. Moreover, any changes occurring during surgery are not accounted for.
Registration of the patient as a reference for determining the position of surgical instruments or probes is known.
In U.S. Pat. No. 5,782,765 (Jonkman), titled MEDICAL POSITIONING SYSTEM, filed in 1996, and incorporated herein by reference, there was disclosed a method and apparatus for positioning a probe inside a patient including a plurality of transmitter/receiver nodes arranged around the patient for communicating with the probe and generating navigation signals, a system for generating one or more positional signals in response to the navigational signals, and a system for collecting and analyzing those positional signals to determine the location of the medical instrument inside the patient""s body. The transmitting/receiving nodes may be arranged on a flexible blanket which is wrapped around and adhered to the patient""s body or over a table supporting the patient""s body.
U.S. Pat. No. 5,871,455 (Bucholz), titled SYSTEM FOR INDICATING THE POSITION OF A SURGICAL PROBE WITHIN A HEAD ON AN IMAGE OF THE HEAD, filed in 1995, suggested a similar approach. There was disclosed a system for determining a position of a probe relative to an object such as a head of a body of a patient. The head includes a surface such as a forehead having a contour. Cross sectional images of the head are scanned and stored as a function of the forehead contour. If the forehead contour does not appear in the scan images, then the position of the forehead contour relative to the scan images is determined with an optical scanner and a ring. During surgery, the optical scanner also determines the position of the forehead relative to the ring. An array for receiving radiation emitted from the probe and from the ring generates signals indicating the position of the tip of the probe relative to the ring. A stereotactic imaging system generates and displays an image of the head corresponding to the measured position of the tip of the probe. The system may also display scan images from different scanning technologies which scan images correspond to the same position in the head (See also U.S. Pat. No. 5,383,454).
It is a main object of the present invention to facilitate the registration of the coordinate set of the scanner to establish the relation to an additional independent coordinate set. This way a definite relation between the two coordinate sets may be established, allowing positioning and location of a certain point in one coordinate set in the other set of coordinates and vice versa.
It is a purpose of the present invention to provide a positioning system and method that refers the coordinate set of the imaging device itself, for example the image coordinate set in an MRI apparatus, by registering the magnet assembly or any other stationary object or object of known location with or in the immediate vicinity of the scanner""s scanned region.
It is yet another object of the invention to provide such method and system for positioning that is independent of the patient""s position within the scanned region.
Another object of the present invention is to provide a positioning method and system that is based on registering the spatial coordinates of the scanner thus allowing the relation of the images obtained after the registration to the exact position of the scanned object. Alternatively, any change in the position of the scanner can be measured as well and related to the coordinates of the object of interest within the image.
A positioning method comprising spatial registration of reference points of known location on an imager in order to perform a highly accurate procedure based on images acquired by the imager. The images are acquired and stored as a function of the position of the patient within the scanner. Moreover, every point within the imaging volume is determinable. The relation between the coordinate set of the scanner and the real physical coordinates is established by registration of several reference points of known location on the scanner, forming a reference space. The center of this registered space and the orientation of the coordinate system of the reference space are known with respect to the center and the direction of the coordinate set of the images acquired by the same imager. Thus the coordinate set of the image has a fixed position in space and can be used to position an object relative to images acquired by the scanner. In another embodiment of the present invention the registration is performed using an array of receiving/emitting/reflecting sources attached to a probe. An adjacent emitting/receiving detection device, whose position and orientation is known in relation to the scanner, is used to obtain the signals determining the coordinates of the scanner.
There is thus provided, in accordance with a preferred embodiment of the present invention, a positioning system for determining the relation between a coordinate set of a scanning apparatus and a coordinate set of a tracking system so as to allow determining the position of a selected target on an image of a patient acquired by the scanning apparatus in the coordinate set of the tracking apparatus and vice versa, the system comprising:
reference points means positioned in predetermined location relative to the coordinate set of the scanning apparatus;
tracking means adapted to detect and determine the position of said reference points means, relative to the coordinate set of the tracking means;
processing means adapted to communicate with said tracking means and adapted to determine the relation between the coordinate set of the scanning apparatus and the coordinate set of the tracking means, and adapted to translate the coordinates of the target on the image acquired by the scanning apparatus to corresponding coordinates on the coordinate set of the tracking means.
Furthermore, in accordance with another preferred embodiment of the present invention, said reference points means comprise markers detectable by said tracking means.
Furthermore, in accordance with another preferred embodiment of the present invention, said tracking means is an optical tracking system.
Furthermore, in accordance with another preferred embodiment of the present invention, said reference points means comprise markers detectable by said tracking means.
Furthermore, in accordance with another preferred embodiment of the present invention, said optical tracking system operates in IR.
Furthermore, in accordance with another preferred embodiment of the present invention, said optical tracking system comprises:
IR transponder adapted to illuminate IR light on said reference points means, and adapted to receive reflected IR light from said reference points means;
analyzing means for analyzing the received reflected IR light digitize it in3D and calculate the position of said reference points means.
Furthermore, in accordance with another preferred embodiment of the present invention, said tracking means comprises detecting means for detecting tracking signal the reference points means and analyzing means for analyzing the detected tracking signal and calculating the position of said reference points means.
Furthermore, in accordance with another preferred embodiment of the present invention, said processing means include coordinate transformation software.
Furthermore, in accordance with another preferred embodiment of the present invention, processing means is further adapted to provide spatial guidance so as to enable positioning of the surgical probe on a predetermined physical target location corresponding to a selected target on the image.
Furthermore, in accordance with another preferred embodiment of the present invention, there is provided a positioning method for determining the relation between a coordinate set of a scanning apparatus and a coordinate set of a tracking system so as to allow determining the position of a selected target on an image of a patient acquired by the scanning apparatus in the coordinate set of the tracking apparatus and vice versa, the method comprising the steps of:
a. providing reference points means positioned in predetermined location relative to a predetermined coordinate set of the scanning apparatus;
b. providing tracking means adapted to detect and determine the position of said reference points means, relative to the coordinate set of the tracking means;
c. providing processing means adapted to communicate with said tracking means and adapted to determine the relation between the coordinate set of the scanning apparatus and the coordinate set of the tracking means, and adapted to translate the coordinates of the target on the image acquired by the scanning apparatus to corresponding coordinates on the coordinate set of the tracking means;
d. determining the position of the reference points means relative to the coordinate set of the tracking means;
e. calculating the position of the reference points means with respect to the coordinate set of the scanning apparatus and determining the transformation matrix between the coordinate set of the tracking means and the scanning apparatus coordinate set; and
f. selecting a target on the image and transforming its position to the coordinate set of the tracking means using the transformation matrix;
Furthermore, in accordance with another preferred embodiment of the present invention, the transformation matrix is a rotation and/or shift transform matrix.